#include<stdio.h>
int main()
{
	int i = 0, sgn = 1, n = 100;
	double sum = 0, ds = 0;
	for (i = 1; i <= n; i++)
	{
		ds = (double)sgn / i;
		sum += ds;
		sgn = -sgn;
	}
	printf("%lf", sum);
}